1. Field of the Invention
This invention relates to a high tension cable device for use with an ignition system in an automobile engine or the like.
2. Description of the Prior Art
An ignition system in an automobile or the like is normally constructed in such a manner as to generate sparks by applying a high voltage to an ignition plug, and heretofore, there has been known an ignition system having a so-called series gap which is provided in series with a spark plug to avoid the problems of plug fouling.
An ignition system having the series gap constructed as above is disclosed, for example, in a Utility Model Application Laid-Open No. 61-101486. This ignition system is constructed as shown in FIG. 5, wherein reference character A denotes an ignition plug which is threadedly engaged with a cylinder head B of an engine, and on the other hand, a high tension cable C is fitted removably on the ignition plug A, which high tension cable C further comprising a plug cap 6 in which a connecting terminal 2 engageable with a terminal 1 of the ignition plug A and a cable terminal 4 connected to one end of a high tension cable 3 are located such that they are facing to each other with a space therebetween, for example, in a cylindrical casing 5. Further, between the connecting terminal 2 and the cable terminal 4 within the plug cap 6, a discharge tube 10 forming a series gap S by sealing a pair of discharge electrodes 7 and 8 into a glass tube 9 is disposed.
An ignition system having a series gap as constructed above requires a discharge tube having a high discharge starting voltage (a high breakdown voltage) for correctly sparking the spark plug even if the plug is fouled, but when a high voltage is supplied, a so-called creeping discharge is likely to occur along the external surface of the discharge tube before starting the discharge at the series gap. In order to prevent the occurrence of this creeping discharge, although another method such as filling an electrically insulating resin in the space between the discharge tube and the casing can be taken, since the ignition system is likely to receive abrupt heating and cooling phenomenon repetitively in accordance with driving operation of the engine, the casing and other devices are likely to be worn out, and in addition, tiny cracks can be generated in the parts where thermal stress is applied, and furthermore, since a grounding instrument is normally disposed in the nearby region of the ignition system, destruction of the insulation or the like may be caused thereby and an ignition failure of the engine can also take place due to the energy loss caused thereby.